Ultra-high data rate digital mm-wave transmitter with energy efficient spectral filtering

Abstract

A digital transmitter architecture is disclosed to transmit (TX) multi-gigabit per second data signals on single carriers (SC) or orthogonal frequency division multiplexing (OFDM) carriers at millimeter wave frequencies in either one of a high-resolution modulation mode or a spectral shaping mode. The architecture includes a number of digital power amplifier (DPA) and modulation reconfigurable circuit segments to process individual bits of a data bit stream in parallel according to a specific circuit configuration corresponding to the selected TX mode using a multiplexer to switch between configurations.

The invention claimed is: 
     
       1. A digital transmitter circuit adapted to transmit a multi-gigabit per second data signal at millimeter wave frequencies, the digital transmitter comprising:
 digital power amplifier (DPA) and modulation circuitry comprising: 
 a plurality of bit-segmented modulation driver circuits arranged in parallel and configured to modulate a digital data signal on an RF carrier to form a transmit (TX) signal in separate amplitude modulation (AM) and phase modulation (PM) paths, the DPA and modulation circuitry containing selectable circuits to form the transmit signal in one of a spectral shaping TX mode or a high resolution modulation TX mode. 
 
     
     
       2. The digital transmitter circuit of  claim 1  wherein when the selectable circuits for the spectral shaping TX mode are configured to filter out-of-band frequencies using analog pulse shaping circuitry. 
     
     
       3. The digital transmitter circuit of  claim 2  wherein analog pulse shaping circuitry comprises a plurality of programmable current starved inverters configured as taps of a finite impulse response (FIR) filter. 
     
     
       4. The digital transmitter circuit of  claim 1  wherein the selectable circuits for the spectral shaping mode are configured to additionally segment each bit into sub-units and delay their phase to provide analog pulse shaping by increasing a bit driver time constants to slow down pulse edges. 
     
     
       5. The digital transmitter circuit of  claim 1  wherein the RF carrier comprises either a single carrier or an orthogonal frequency division multiplexing (OFDM) carrier. 
     
     
       6. The digital transmitter circuit of  claim 1  wherein each modulation and driver circuit includes power amplifier (PA) cells each comprising two differential field effect transistors (FETs) coupled at their gates to ground by a tail device and a capacitive neutralization circuit distributively coupling a source of a first FET of the PA cell to a drain of a second FET and a source of the second FET to a drain of the first FET. 
     
     
       7. The digital transmitter circuit of  claim 1  wherein the modulation driver circuits further comprise linear feed forward equalizers to either predistort a TX data signal in a time domain for modulating a single carrier (SC) or predistort inverse fast Fourier transform (IFFT) block sets in a frequency domain for modulating an orthogonal frequency division multiplexing (OFDM) carrier. 
     
     
       8. A device for a transmitter having digital transmit (TX) circuitry to transmit a multi-gigabit per second data signal at millimeter wave frequencies, the device comprising a memory storing machine executable instructions; and
 a processing circuit including at least one processor to retrieve and execute the machine executable instructions and cause the at least one processor to: 
 identify a mode of transmission to transmit between a spectral shaping TX mode or high resolution TX mode; and 
 signal the transmitter and cause the digital TX circuitry to:
 amplify and modulate a digital data signal on an RF carrier to form a transmit signal using a plurality of separate and parallel bit-segmented amplitude modulation (AM) and phase modulation (PM) reconfigurable driver circuits; and 
 select a configuration of the reconfigurable driver circuits to form the transmit signal based on the identified mode of transmission. 
 
 
     
     
       9. The device of  claim 8  wherein the reconfigurable driver circuits for the spectral shaping mode are configured to filter out-of-band frequencies using analog pulse shaping circuitry. 
     
     
       10. The device of  claim 9  wherein the analog pulse shaping circuitry comprises a number of phase shifted sub-bit branches, each branch providing a sub-bit having a different phase to a programmable current starved inverter and configured as taps of a finite impulse response (FIR) filter. 
     
     
       11. The device of  claim 8  wherein the reconfigurable driver circuits for the spectral shaping mode provide analog pulse shaping by increasing resistor-capacitor (RC) circuit time constants in select driver circuits to slow down pulse edges and filter out of band (OOB) frequencies. 
     
     
       12. The device of  claim 8  wherein the RF carrier comprises either a single carrier or an orthogonal frequency division multiplexing (OFDM) carrier. 
     
     
       13. The device of  claim 8  wherein each reconfigurable driver circuit includes a power amplifier (PA) cell comprising differential PA devices coupled to a tail switching device and a distributed capacitive neutralization circuit and wherein the memory includes further machine readable instructions to cause the one or more processors to signal bits to the tail switching device. 
     
     
       14. The device of  claim 8  wherein the reconfigurable driver circuits include linear feed forward equalizers (FFEs) to predistort TX data signals in a time domain for modulating a single carrier (SC) or predistort inverse fast Fourier transform blocks in a frequency domain for modulating an orthogonal frequency division multiplexing (OFDM) carrier to further reduce of out of band frequencies and limit error vector magnitude (EVM). 
     
     
       15. A user equipment (UE) comprising:
 a digital transmitter including transmit circuitry configured to transmit a multi-gigabit per second data signal modulated on an RF carrier at millimeter wave frequencies and reconfigurable to form a transmit (TX) signal in either one of a high-resolution modulation TX mode and a spectral shaping TX mode; and a transmit mode control circuit communicatively coupled with the digital transmitter and configured to signal the digital transmitter to select which TX mode to use, the transmit circuitry comprising a number of digital power amplifier (DPA) and modulation reconfigurable circuit segments to process the data signal on a per bit basis in parallel, to form the TX signal according to the selected TX mode. 
 
     
     
       16. The UE of  claim 15  wherein the reconfigurable circuit segments include analog pulse shaping circuitry to process the data signal in the spectral shaping TX mode. 
     
     
       17. The UE of  claim 16  wherein the analog pulse shaping circuitry comprises a plurality of programmable current starved inverters serving as tap strengths of a finite impulse response (FIR) filter. 
     
     
       18. The UE of  claim 17  wherein the reconfigurable circuit segments in the spectral shaping TX mode are configured to suppress out-of-band frequencies by slowing down pulse edges. 
     
     
       19. The UE of  claim 15  wherein the RF carrier comprises either a single carrier or an orthogonal frequency division multiplexing (OFDM) carrier. 
     
     
       20. The UE of  claim 15  wherein at least one of:
 each reconfigurable circuit segment comprises a power amplifier (PA) cell comprising differential PA devices coupled to a tail switching device and a distributed capacitive neutralization circuit, 
 the reconfigurable circuit segments are configured to predistort a TX data signal in a time domain for modulating a single carrier (SC) or predistort inverse fast Fourier transform (IFFT) block sets in a frequency domain for modulating an orthogonal frequency division multiplexing (OFDM) carrier, 
 the digital transmitter further includes digital to analog circuitry to provide a data bit stream to the transmit circuitry, or 
 the reconfigurable circuit segments further comprise a plurality of multiplexers to enable switching between finite impulse response (FIR) circuitry used in the spectral shaping TX mode and bypassing FIR circuitry not used in the high-resolution modulation mode.